Abstract : A numerical investigation of head-on collisions of solitary waves in water shows that they reform to be solitary waves almost as before the collision, but not quite. A little energy is deposited in a dispersive wave train generated during the collision. Hence, solitary waves in water are not exactly solitons. The calculations further indicate a transition where the water at the crest attempts to fly off the surface when an identical pair of incoming waves have an amplitude/depth ratio exceeding approximately 0.45. (Author)